“Clathrates” generally refer to non-stoichiometric metastable substances in which lattice structures composed of first molecular components (host molecules) trap or encage one or more other molecular components (guest molecules) in what resembles a crystal-like structure. Clathrates are sometimes referred to as inclusion compounds, hydrates, gas hydrates, methane hydrates, natural gas hydrates, CO2 hydrates and the like.
In the field of hydrocarbon exploration and development, clathrates are of particular interest. For example, clathrates exist in which water host molecule lattices encage one or more types of hydrocarbon guest molecule(s). Such hydrocarbon clathrates occur naturally in environments of relatively low temperature and high pressure where water and hydrocarbon molecules are present, such as in deepwater and permafrost sediments. Clathrates at lower temperatures remain stable at lower pressures, and conversely clathrates at higher temperatures require higher pressures to remain stable.
It has been shown theoretically and experimentally that clathrates form preferentially in sediments with larger pores. This phenomenon has been ascribed to the Gibbs-Thomson effect, which suppresses nucleation of solids in restricted spaces like the pore space of fine-grained sediments. The Gibbs-Thomson effect may be used to explain observations of clathrate distribution in marine sediments of different grain sizes. However, existing work investigating the Gibbs-Thomson effect has focused solely on explaining reasons for a known presence of clathrates in terms of pore size. A more useful description for geophysical prospecting would be in terms of porosity. However, the relationship between porosity and pore size is complicated and depends on grain shape and packing.
As such, improvements in methods and systems for detecting whether conditions exist for formation of clathrates would be desirable, in particular in the area of hydrocarbon exploration.